Modern vehicles are equipped with a large number of controlled devices and sensors, such as a controlled brake system, a controlled steering system, and a controlled suspension system. Usually, each of these devices has an ECU of its own, which compares the measured actual values with predetermined nominal values and outputs output signals corresponding to the result of comparison. The control performance of the individual devices, in turn, can depend on the condition of other controlled devices. Thus, the performance of the controlled steering system can e.g. depend on the condition of the suspension system or on the actual value calculated by the ECU of the suspension system, respectively. It is this way possible that when the vehicle drives at low sped on a poor road surface, a change of angle of the steering wheel can cause a much more significant change of the steering angle than is the case when the vehicle drives quickly on a plane road. Thus, all or a large part of the individual devices and sensors are cross-linked. There is an exchange of information between the ECUs of the individual devices by way of a network. This network allows e.g. transmitting measured values such as the rotational speed of the motor, the acceleration of the vehicle, the yaw angle of the vehicle, the tire pressure, the slip of the tires, the steering angle of the vehicle, the speed of the vehicle relative to the ground, the engine or wheel rotational speed, the temperature of oil and cooling water, the acceleration, and the yaw rate.
In general, only a few of these pieces of information conveyed in the mentioned network will be displayed to the driver on the instrument panel of the vehicle. The display of such information is often limited to the temperature of the cooling water and the speed. It is, however, in many cases desirable for the drivers of vehicles to have access to additional information exchanged in the network, which under certain circumstances may considerably go beyond the information that is made available to the driver on the instrument panel in the vehicle supplied by a manufacturer. This applies, for example, to drivers being interested in knowing which values e.g. the engine or the rotational speed, the oil temperature, the acceleration, and the yaw rate will adopt during driving, or how a vehicle behaves in certain situations in traffic and which values individual parameters will adopt then, such as the length of a stopping distance when braking on a defined underground.
In view of the above, an object of the invention involves providing the driver of a vehicle with additional information about the state of the vehicle, going beyond what is typically offered to the driver on instrument panels in the vehicle. This access to information exchanged in the network shall be possible retroactively, i.e. after delivery of the vehicle. To allow this retroactive access to information, there is need for a device tapping the information from the vehicle network, without modifying the cabling of the vehicle, since an intervention into the cabling of a motor vehicle, unless this action is taken by an expert, can lead to lapse of the general type approval for this vehicle. Another objective of the invention is that the retroactively arranged extraction of the desired information will definitely not inhibit or even modify the information flow in the network so that the extraction of information is negligible with respect to its effect on the data flow in the network.